LABORATORY MEASUREMENTS OF A STEADY BREAKER USING PIV AND BIV

Chang Lin, Shih-Chun Hsieh, I-Ju Lin, Kuang-An Chang, Rajkumar Raikar

Abstract

Image-based particle image velocimetry (PIV) and bubble image velocimetry (BIV) techniques were employed to measure the flow field in both the non-aerated and aerated regions in a steady hydraulic jump. The jump has a Froude number of 4.62 with a large amount of air entrainment. The mean velocities and turbulence properties were obtained by ensemble averaging the repeated measurements. The spatial variations of mean velocity profiles, turbulent intensity, and Reynolds stress were discussed in details. The results show that the ratio between the maximum bubble velocity and the maximum water velocity is almost constant with a value about 0.6. The turbulence intensity of bubbles is very high in the aerated region and reaches about 0.4, while the turbulence velocity of water below the roller is significantly lower. The Reynolds stress is mostly negative and increases as elevation increases. The maximum Reynolds stress occurs at the free surface.